Known in the art are phenol-formaldehyde, polyester and epoxy resins employed as binders for the manufacture of foamed plastics, laminated plastics, graphitized plastics, compression-moulding powders, spray-deposited coatings. However, said resins do not satisfy the requirements imposed on the final articles in respect of their heat-resistance and chemical resistance. Furthermore, powder-like resinous products based on epoxy and polyester resins are rather expensive.
Known in the art is a process for producing powder-like furan resins comprising heating a ketone of the furan series such as crystalline difurfurylidene acetone at the temperature of 220.degree. C. for 6 hours. The resulting resin is stable against the effect of aggressive media at temperatures of at most 80.degree. C. Furthermore, Martens yield temperature of the prior art resin does not exceed 250.degree. C. The desired product yield ensured by the prior art process is only 45 to 55%. Moreover, the resin produced by said process is not stable against oxidizing agents. The thus-produced resin is suitable only for the manufacture of a construction graphite-reinforced plastic.
Also known in the art is a process for producing powder-like furna resins comprising heating difurfurylidene acetone in a current of an inert gas at the temperature of 200.degree. C. for the period of 4 hours. The resulting resin has but a limited resistance in respect of aggressive media; it is not resistant against oxidizing agents and its Martens yield temperature does not exceed 270.degree. C. The desired product yield in this process is equal to 70%. This process is also suitable for the manufacture of resins for a construction graphite-reinforced plastic.
It is an object of the present invention to overcome the above-mentioned disadvantages.
It is also an object of the present invention to provide such a process which would enable the production of a powder-like furan resin possessing an increased chemical resistance relative to the effect of highly-aggressive media and oxidizing agents at elevated temperatures.
It is another object of the present to provide such a process which would make it possible to produce a powder-like furan resin possessing high yield temperature.
It is still another object of the present invention to provide such a process for producing a powder-like furan resin which would enable a high yield of the desired product.
These objects are accomplished by that in the production of a powder-like furan resin by way of heating a ketone of the furan series, in accordance with the present invention, the process is conducted at a temperature within the range of from 130.degree. to 200.degree. C. in the presence of a phenol-formaldehyde resin, the weight ratio between said ketone of the furane series and said phenol-formaldehyde resin is 10:3-15 respectively.
The process for producing a powder-like furan resin makes it possible to obtain a resin possessing an increased resistance to the effect of highly-aggressive media at a temperature of up to 120.degree. C. and oxidizing agents at a temperature of up to 80.degree. C. with a Martens yield temperature as high as 300.degree. C. The resin yield is ensured at about 93%.
To reduce the process duration down to 1-2 hours, it is advisable to maintain the process temperature, in accordance with the present invention, within the range of from 180.degree. to 200.degree. C.
Besides, in accordance with the present invention it is also advisable to use, as the ketone of the furan series, monofurfurylidene acetone, difurfurylidene acetone, a mixture of monofurfurylidene acetone and difurfurylidene acetone in a ratio therebetween of from 7:3 to 7:7 respectively, difurfurylidene cyclohexanone, 1,9-di-(.alpha.-furyl)-nonanetetraen-1,3,6,8-one-5, 1,5-di-(.alpha.-furyl)-2,4-dimethylpentadien-1,4-one-3 or mixtures thereof.
The use of ketones belonging to the furane series or mixtures thereof makes it possible to perform the process for producing a furan powder-like resin of various grades thus imparting thereto a whole range of specific properties for a further processing thereof to articles. Depending on the field of application of a resin, the latter is produced with a required melting point or dropping point.
To produce a furan resin suitable for the manufacture of coatings, compression-moulded articles, construction materials in accordance with the present invention it is advisable to conduct the process at a temperature within the range of from 130.degree. to 180.degree. C. in the presence of furfurol at a weight ratio of the furan-series ketone, phenolformaldehyde resin and furfurol ranging from 10:3:2 to 10:15:5 respectively.
The resin produced by the process according to the present invention is stable against highly-aggressive media at elevated temperatures, its Martens yield point is as high as 320.degree. C., and impact strength is up to 4 kgf.cm/cm.sup.2.
An embodiment of the present invention resides in that the process is performed at a weight ratio of the furan-series ketone, phenolformaldehyde resin and furfurol equal to 10:5:5 respectively at the process temperature varied within the range of from 130.degree. to 140.degree. C.
Owing to the present invention it is now possible to produce a furan resin suitable for the production of a structural graphite-reinforced plastic, a laminated plastic.
Incorporation of furfurol into the reaction mixture makes it possible to lower the process temperature down to 130.degree.-140.degree. C. In accordance with the present invention, it is advisable to perform the process in the presence of 1-3% by weight of a catalyst (calculated for the weight of the starting components) comprising a mixture of tin dichloride and hexamethylene diamine employed in a weight ratio of from 7:3 to 3:7 respectively. Performance of the process in the presence of the catalyst makes it possible to reduce the process duration down to 1-3 hours.
In order to impart the property of non-inflammation or self-extinction to the resin, it is advisable to incorporate, into the starting mixture of the components, triphenylphosphate taken in a weight ratio of the ketone of the furan series of from 10:0.5 to 10:3 respectively.
To increase impact resistance of the resulting resin by 1.6 times, it is advisable, in accordance with the present invention, to conduct the process in the presence of tetraethoxysilane taken in a weight ratio to the ketone of the furane series within the range of from 10:3 to 10:6 respectively.